DB_ENV->lock_detect()

#include <db.h>

int
DB_ENV->lock_detect(DB_ENV *env,
    u_int32_t flags, u_int32_t atype, int *rejected);

The DB_ENV->lock_detect() method runs one iteration of the deadlock detector. The deadlock detector traverses the lock table and marks one of the participating lock requesters for rejection in each deadlock it finds.

The DB_ENV->lock_detect() method is the underlying method used by the db_deadlock utility. See the db_deadlock utility source code for an example of using DB_ENV->lock_detect() in a IEEE/ANSI Std 1003.1 (POSIX) environment.

The DB_ENV->lock_detect() method returns a non-zero error value on failure and 0 on success.

Parameters

flags

The flags parameter is currently unused, and must be set to 0.

atype

The atype parameter specifies which lock request(s) to reject. The deadlock detector will reject the lock request with the lowest priority. If multiple lock requests have the lowest priority, then the atype parameter is used to select which of those lock requests to reject. It must be set to one of the following list:

DB_LOCK_DEFAULT

Use the default lock policy, which is DB_LOCK_RANDOM.
DB_LOCK_EXPIRE

Reject lock requests which have timed out. No other deadlock detection is performed.
DB_LOCK_MAXLOCKS

Reject the lock request for the locker ID with the most locks.
DB_LOCK_MAXWRITE

Reject the lock request for the locker ID with the most write locks.
DB_LOCK_MINLOCKS

Reject the lock request for the locker ID with the fewest locks.
DB_LOCK_MINWRITE

Reject the lock request for the locker ID with the fewest write locks.
DB_LOCK_OLDEST

Reject the lock request for the locker ID with the oldest lock.
DB_LOCK_RANDOM

Reject the lock request for a random locker ID.
DB_LOCK_YOUNGEST

Reject the lock request for the locker ID with the youngest lock.

rejected

If the rejected parameter is non-NULL, the memory location to which it refers will be set to the number of lock requests that were rejected.

Errors

The DB_ENV->lock_detect() method may fail and return one of the following non-zero errors:

EINVAL

An invalid flag value or parameter was specified.

Class

DB_ENV, DB_LOCK